Reenforced concrete joist



Feb. 5, 1935. H. F. YoUNG REENFORCED CONCRETE JOIST INVENTOR Hoym/TY BY@ ATTORNEYS Filed Deo. l5, 1932 Patented Feb. 1.935

, "Young'aaministvrafrix of said. Reward n yungl f f l"ingiaa'substantiallyiiatf-upperportion'Z-on-which y "First, toprovideiai-'precastreenfrcedwconcrete the iifooriSIabfis-received. vJlIh'e'headat the 'edges ij oist for. .uses-in Lfloor-or-Lroof;y constructionliwhioh of-ffthis-fsurface' '7' `has substantially `vright ffangle v:joistfsmaybe joined/.totthe .oorforsroofslab-.vwith portions 8 to4 allow close fitting o'f'the formhused 25 "acement4to4cement-b'ond toformfarflbeam'fcon# -ineonstructingf a'poured` sl'ab fther'eon. fThe'vlat :5 ,struction nin-whi'c':hfthef-slab.formsfrtheJprincipal -portion"7 :islsomewhatlarger 'thanwthe base"9 of :compression lzmember twithout'dependingV upon the joist although this is unnecessary, the' object lanyother bonding. i f y 1 1 being-ime'r'elyto make a flat top'area -onlthehead .Secondz-to provide suchfaijoi'stzde'sig-ned withia ioffthe'joistloffsuiiicientfareatoijointothelfslab headofashapeandzsizezto'zjoimto.the.slabzwith with@ cement-to-cement vbond without#other 10 only a cement-to-cement bond. zreenrorcing means, such as pro-jectingmetal shear Thiritoproyidesuch:a1-joisttthatnnay be used members. The-base of myjoist issmaller because iinrsimpleffsp'anssor:1in 'constructions-embodying itr isfldesignedto have-merely' the kproper) cross cantileverfaction overjrbeams ornwvalltsupports@ section `andany excess would'be-waste.

"The objectsff:th'siinventiorware:

'T15 `Fourthto .providezfsuchga :jist"that':may'be "Inpouringa slab onforms,'"the -forms aref'fl'tted 15.

,ijoine'dttotthefoorislabrwithzfonly acementstobetween thejoists andsupported-bysuitable stircementvbondfwithoututhe necessityc'of 'embracing lrups'onshoringand thefrods yare laidand'the ithevhead:of.the'joistiinthesslab bymrovidingiaat slab 2-is-poured. 'The wetfconcr'eteY bondsftofthe etopxlareawofwsuincientasize:.to-ibondz@toixand.'with- `hat top I7 of fthe joists, making a cement-to` standrithe shear`-stresses::normallylplacedffon.the 'cementlbond between the joistand the slab,-form 2O zconstructionzbyf'l'.:beamgaction y f ,g s ingfasubstantialmonolith-inwhioh the joist'forms Objects relatingtoafdetailsarandffeconomies .of fthe ltension member 'and the'slab the principal my invention will appear from the description vcompression member.- tof-fllowgf Theinvention is defined and pointed "Thefloor-slabfisunitedtothe-joist byacementout in the claims. A structure which is a preto-cement bond and gives complete T-beam 5 ferred embodiment of my invention is illustrated action, the slab acting as the principal compresin the accompanying drawing, in which: sion member in the completed construction. The Fig. 1 is a perspective view of .a construction joist can be easily made in upright forms and embodying my joists. when thus formed the surface 'l is rough and as- Fig. 2 is a sectional View of a slab poured on sists materially in the bonding. i y 0 forms and joined to one of my joists. In Fig. 3 I show my precast joists used in a v Fig. 3 is a sectional view of a Afloor slab cast iioor construction over a girder support 10 with n j on my joists and embodying cantilever action or a rod 11 cast in the slab and substantially parcontinuity. allel to the joists and extending over the'beam Referring to the drawing, 1 is my reenforced to provide cantilever action or continuity.'` In the 35 concrete precast joist. 2 is a structural floor slab construction shown, the ends of the joists are cast of reenforced concrete having reenforcing rods 3 in the girder to form a monolithic construction. and joined to the joists to give T beam action. It will be understood that my construction can The joistsl havereenforcingrods4 and 5 andmay also be used over an interior bearing wall in be formed of any concrete mixture. I have found which the ends of the joists are firmly embedded that the use of the so-called light weight aggrein masonry. The surface:- 7 on the head of the gates, such as cinders or Haydite, which is a joist is of suicient size to resist the added shear ground slag aggregate, are of great utility beaction incident to the cantilever action. It will cause of the light weight and the ability to absorb be seenu that in this construction the slab forms 40 the bonding cement to form a very complete bond the principal compression member in the area to the slab. With my construction, the joists of positive movement and isvin tension in the may be made of such strength that the joists alone Y area of `negative movement adjacent the support. will not support the designed iioor load until the In an 8.6 joist, which is a joist having an 8-inch slab is joined thereto to form the compression depth and ja. .6-inch crosssectional steel reenmember. This makes possible the use of much forcement, I use a hat surface 'l that isve rinches 0 lighter joists with a resulting saving in matein width and nd that such a joist is suitable for rial. It will be understood that the joists can all'types of construction work in which such a be made strong enough to support the load if it joistcould be used. In a 12'foot`length, which is so desired. is substantially the shortest length used and in ,55 My joist is provided with a flaring headG havwhich the shear is the greatest, this joist at 24 inches spacing will support a 240-poundload to the square footof floor. Of this 24U-pound load,

" 40 pounds is dead weight and 200 pounds is live,

foot `joist of this size the *shear averages S16-'7(- pounds to the linear inch and is of a maximum value of 333 pounds per linear inch. In a cantilevercons'truction a 50 percent .increase shows 500 pounds per linear inch shear value. l With these figures, the design allowing 100-pounds'peiV square inch shear will require a 5"-ivnch head on the joist.

It wi11 be obvious to those skued in maart for dierent loads and different span or depthf'f joist,dierent'sh ear values are easily computed and that the size-'ofthe head [to-which the slab is cemented witha cement-to-cement bondrmay `be ,easily determined. f

. yHaving thus described myfinvention,` what I *claim*A as newand desire to secure vby Letters Patent is: Y

1.'In a floor constructionor the like, a plu'-` rality of precastreenforced concrete joists, each having a head having `a substantial flat bearing area adapted to receive a structural reenforced concrete slab to -fcrm a T` beam construction,

said area being of arsize to*v bond to said slab with only a cement-to-cement bond of a strength to' resist the shear stresses between the joists `and. thelslab incident to T beam` construction in `which the slab is the principal compression member, and a structural reenforced concrete slab on said bearing areas of vjoists and joined to said bearing area with a cement-to-cement bond, with- -out metallic reenforcing or bonding members extending fromsaid joists and penetrating the joint between said joists and said slabrto form amonolithic Tr beam construction in which the slab forms the principal 'compression' member. c 2. In a oor construction or the like; a plurality of precast reenforced concrete `joists, each having a head having a substantial bearing areal adapted to receive a structural reenforced concrete slab toy form a T beam construction and having an area of a'size to bond to said slab with only a .cement- .tpV-cementbond ,01:A a strength to resist the shea;` stresses :between :the joists and the slab incident to VT beamcon'struction in which the slab forms the principal compression member,

and a structural reenforced concrete slab on said .joists joined'toisaid bearing area thereof withy a cement-to-cement bond, without metallic reenforcingforbonding members extending from said joist's and 'penetrating the' joint between said joists and said slab to form a monolithic T beam v-constructi'o'ni ix'igvvliich'l the slab forms the principal compression member. y

3. Av precast reenforced concrete joist having a head with;afsubstantialfatbearingarea. with- .out projectingmeta,lreenforcing or bonding :meanspand adapted tofreceivea slab to formpa YT beam-z construction; said area being of a size tobond tota structural reenforced concrete'slab bearing thereon with-a cement-to-cement bond of 4a strength to" resistr shear stresses, Without projecting metal, at the point of. bonding incident .to the use of said joist in T` beam construction in' which the slab forms the principal compres'- sio'n member. f A v .4. A precast .reenforcedi concrete kjoist having c l 'a head. without projecting metal reenforcing or bondingmeans and withua substantial bearing area adapted "to receive a'slab,y saidarea being of a size to bond to al structural reenforced concrete slab bearing thereon with a cementp vto-cement bond .of c ar strengthv to .resist shear stresses, without projecting'metal, at the point oibonding incidentto the use of` said joist in T beam construction'in which the 4slab fiorms the principal compression member. l f

HOWARD F. YOUNG. l, 

